Chris V,
Hopefully you can help. I have a 1979 Johnson 100hp Javelin that was sitting for a few years. The carbs were clean and I changed the impellor. I put fresh gas/oil in it and ran it for about twenty minutes on muffs. The water was not coming out of the left exhaust bank as well as the right, but I thought it was ok (wrong). I then put the boat in the water and it ran fantastic for about 15 minutes. Then while turning 3700 RPM it shut down and it was obvious the left cylinder bank had overheated. I can turn the engine by hand and feel compression on all cylinders. The first thing I will do is change both thermostats as this is what caused the overheat. I have a couple questions. When the motor shut down it killed all electric power to the motor and tilt/trim. How do I restore electic power to the engine? What steps should I take after an overheat (re-torque head bolts, inspections, compression test, new head gasket, etc). Last question…is the motor toast?
I appreciate any help you can give to fix my dumb mistake.
i’m not chris but sure sounds like the fuse thats on the motor is blown. overheating wouldn’t keep the trim from working. that model had a audible horn in the control box. did it go off?
green grass and high tides forever
jhp----- Murrells Inlet
Not chris either… but agree w/ tideline. It may have overheated, but what you desribe does not sound like over heating. Did the over heat horn sound? Was it blowing steam?
So far, sounds electrikcal to me.
17’ Henry O Hornet
26’ Palmer Scott
No horn, nothing, but definitely an overheat on the left cylinder bank…discolored paint, a little bit of melted plastic, smoking hot, etc. But the engine did not seize. It was running at 3700 rpm and then shut itself off. I agree on the main fuse and will check it out on Monday…stay tuned.
Entropy
Pathfinder 2400V w/Honda 225
If you are positive it was an overheat. Check the compression…will probably be low then you will want to check the rings and cyinder walls.
When you get it fired up again, don’t run the engine if there is no water going through block. Check for blocked passages (screen at water pick-up, in thermostats, in pee tube coming off block). When the engine overheated, you probably lost continuity in a wire due to the heat…check all wires for signs of melting etc…
If spend enough time and money on a motor…it will never be “toast”
Mike
14’ Polarkraft 25 rude
17’ Hydrasports basser, project pictures coming
Wellcraft 250 Sportsman, complete transom replacement, pictures coming soon
sorry guys
been down for a week with the flu.
there isnt anything that would cause the symptoms you are describing, from an overheat, unless the overheat melted a wire.
the t-stats are somewhat difficult on those motors, especially if it has the “bubble” exhaust, not sure if the 100 has it or not.
before going any farther, you need to do a compression test, with a gauge.